boxer having head tremors

[bowsrboxrs]

I have a 1 1/2 year old female boxer.  I took her to a neurologist yesterday because she is having head tremors.  They want to have an Mri done as well as a spinal tap.  My husband and I do not know what to do because it is going to be over 2.000 dollars. We want to know what is wrong and to help her.  If anyone has input please help.